1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a turbine stator vane with a serpentine flow cooling circuit.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, a high temperature gas flow is created in a combustor and then passed through a turbine, typically having a plurality of stages of vanes and blades, in order to convert the energy from the heated gas into mechanical work by driving the rotor shaft. In an aero engine used to power an aircraft, the rotor shaft is used to drive the fan and provide propulsion for the aircraft. In an industrial gas turbine (IGT) engine, the rotor shaft drives an external electric generator to produce electric power. In either engine, the efficiency can be increased by passing a higher temperature gas into the turbine. Since the first stage airfoils (the vanes and blades) are exposed to the hottest temperature gas, these airfoils are critical in determining the turbine inlet temperature, or TIT.
The highest temperature in which the first stage airfoils can operate is dependent upon the material properties and the amount of cooling provided by the compressed cooling air from the compressor. Without any change in the materials used, these airfoils can be exposed to higher temperatures by improving the cooling capability. Therefore, higher gas temperatures can be used if the cooling capability of these airfoils is increased.
FIGS. 1 and 2 show one prior art turbine vane with a serpentine flow cooling circuit. U.S. Pat. No. 5,488,825 issued to Davis et al on Feb. 6, 1996 and entitled GAS TURBINE VANE WITH ENHANCED COOLING discloses a turbine vane with a serpentine flow cooling circuit having a 5-pass aft flowing serpentine for the vane airfoil section, also, individual ID and OD endwalls cooling circuit, two ID and OD turns, skew trip strips for all serpentine cooling passages, cooling air feed through the airfoil leading edge passage from OD endwall, trailing edge discharge cooling slots, and a jumper tube for the delivery of cooling air to seal the housing for ID endwall cooling and purge air.